# Full text of "Handbook Of Chemical Engineering - I"

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```THE TRANSPORTATION OF LIQUIDS
119
To test the fundamental equation we will substitute therein the above computed
values: and find the speed:     ______________________________________
ua = 8.56 -^ 2 tan 18.5° + V32.2 X 168 V 0.685 + (8.56 -*• 2 tan 18.5°)2 = 102.6 ft. per second.
The calculated shut-off head would be H»
102.62
= 164 ft. while the
20        64.4
actual shut-off head was 189 ft. showing that the above rule is only approximate. The hydraulic efficiency is the ratio of the useful power delivered in the water ( = WH) to the power delivered to the water by the impeller. The latter is equal to the torque multiplied by the angular velocity w. The torque is the mass W/g multiplied by the radius r« and the tangential component ua — q of the absolute velocity wa, see Fig. 11. Hence,
Eh = WH +
- q)w = Hg + (ua - g)ua
Approximate rules: For short vanes, or open impellers: Eh = 30 per cent, for Volute Pumps Eh = 50 to 60 per cent, for Turbine Pumps Eh = 57 to 69 per cent.
TABLE 2. — APPROXIMATE RELATION BETWEEN vr/ua and aa